feat(crm): frontend code — pages + services + components

Brings in the full frontend CRM stack: admin authoring pages,
customer-portal surfaces, public response flows, typed services,
and the supporting component library. i18n locale JSON is the next
commit (kept separate so reviewers can read it as data).

Pages
  - Quotes: list / editor / detail / public accept-decline
  - Invoices: list / editor / detail / public payment-check
  - Contracts: list / editor / detail / block library / public sign
  - Calendar (FullCalendar — admin-only v1)
  - Tax report (period picker + CSV/PDF export)
  - Hours (logged time entries, per-customer)
  - Deals lineage (DocumentLineageCard surfaces)
  - CRM Development (admin dev tools, gated by crmDevelopment flag)
  - Customer-portal pages for quotes / invoices / contracts
  - Settings reorg: CRM-Settings group + dedicated tabs for Business
    Profile, CRM behaviour, Contracts block library, Reminder emails
  - BrandingPage typography (PDF font picker)
  - EventDetailsPage / CustomerDetailPage / CreateEventPage extensions
    (event-time fields, hours toggle, per-event reminder override)

Services (typed)
  - quotes.service, bills.service, contracts.service
  - customerAdmin.service, deals.service, calendar.service,
    taxReport.service, contracts-blocks.service
  - businessProfile.service (timezone, font picker, bank accounts)
  - useInstallmentDefaults hook, useLocalizedDate dateInputLang extension

Components (admin)
  - CustomerPicker (shared across quote/invoice/contract editors)
  - LineItemsTable (hierarchy + details_text, memoised pricing)
  - InstallmentsPanel (simple + advanced toggle, fixed-date vs trigger)
  - DocumentLineageCard (deal_uuid grouped view)
  - EditInstallmentPlanModal (atomic post-spawn plan reshape)
  - EventReminderOverrideCard, EmailTemplateEditor (tiptap),
    PdfFontPicker, IntegrityCheckCard
  - Feature-flag context + RequireFeature wrapper + AdminSidebar
    featureFlagsAny derivation + UI-hiding sweep

Build infra
  - vite.config: fullcalendar chunk carved off (~200 KB lazy-loaded)
  - frontend/package.json: tiptap, fullcalendar, signature_pad,
    react-international-phone, et al.
  - tailwind + prose styles updated for editor surfaces

3-way merge note: 1 conflict (CustomerDetailPage.tsx) hand-resolved
to keep upstream's SUPPORTED_LANGUAGES.map() data-driven pattern
over feat/crm's hardcoded option list; feat/crm's DecimalInput
import preserved alongside.

frontend/src/services/email.service.ts

@@ -91,6 +91,22 @@ export const emailService = {
     await api.put(`/admin/email/templates/${key}`, data);
   },
 
+  /** Create a new email template. Used by ReminderTemplatesPage to
+   *  spawn a per-event-type reminder (e.g. `event_reminder_wedding`)
+   *  initialised with the default catch-all's content. Returns 409 if
+   *  the key already exists. */
+  async createTemplate(payload: {
+    template_key: string;
+    translations: Record<string, EmailTemplateTranslation>;
+    category?: string;
+    subcategory?: string;
+    feature_flag?: string;
+    variables?: string[];
+  }): Promise<{ template_key: string; id: number }> {
+    const response = await api.post<{ template_key: string; id: number }>('/admin/email/templates', payload);
+    return response.data;
+  },
+
   // Preview email template
   async previewTemplate(key: string, previewData: Record<string, string>, language: string = 'en'): Promise<EmailPreview> {
     const response = await api.post<EmailPreview>(